1. Field of the Invention
The present invention relates to an automotive alternating-current dynamoelectric machine to which is mounted a stator provided with: a stator core in which slots are formed at a nonuniform pitch at a ratio of two slots per phase per pole; and a three-phase stator winding in which winding phase portions are each formed by zigzag-connecting first and second stator winding phase sub-portions installed in adjacent slot groups.
2. Description of the Related Art
In recent years, improvements in power output are being demanded of automotive alternating-current dynamoelectric machines due to increases in automotive vehicle loads while on the other hand, automotive vehicle engine compartments are becoming increasingly smaller, leaving little mounting space to spare.
In Japanese Patent Laid-Open No. 2002-169490 (Gazette), an automotive alternating-current dynamoelectric machine is disclosed which achieves compactness and high output by forming a stator winding using a plurality of conductor segments, forming twice the usual number of slots in a stator core, and connecting together conductor segments from different layers of different slots to achieve reductions in resistance in the stator winding by increasing space factor and improving cooling.
In this conventional automotive alternating-current dynamoelectric machine, slots are formed in a stator core at a uniform angular pitch (an electrical angle of 30 degrees) at a ratio of two slots per phase per pole. Specifically, the slots constitute six slot groups having different electrical angular phases. If the number of magnetic poles in the rotor is sixteen, there are ninety-six slots.
Slot Numbers 4, 10, 16, etc., through 88, and 94 form a first slot group, and Slot Numbers 5, 11, 17, etc., through 89, and 95 form a second slot group. Slot Numbers 6, 12, 18, etc., through 90, and 96 form a third slot group, and Slot Numbers 1, 7, 13, etc., through 85, and 91 form a fourth slot group. Slot Numbers 2, 8, 14, etc., through 86, and 92 form a fifth slot group, and Slot Numbers 3, 9, 15, etc., through 87, and 93 form a sixth slot group.
The first slot group and the second slot group accommodate an X-phase winding phase portion. The third slot group and the fourth slot group accommodate a Y-phase winding phase portion. The fifth slot group and the sixth slot group accommodate a Z-phase winding phase portion.
A stator winding 110 is constructed by Y-connecting the X-phase winding phase portion 110X, the Y-phase winding phase portion 110Y, and the Z-phase winding phase portion 110Z, as shown in FIG. 23.
In the stator core, pairs of U-shaped conductor segments are accommodated in pairs of slots six slots apart (corresponding to a pitch of one magnetic pole). Twelve wave windings each functioning as a unit winding making one round of the stator core are constructed by connecting in series the conductor segments accommodated in the pairs of slots six slots apart. In other words, two wave windings are accommodated in each of the slot groups.
Now, two wave windings 100a and 101a are accommodated in the first slot group, and two wave windings 100b and 101b are accommodated in the second slot group. The wave winding 100a accommodated in the first slot group and the wave winding 100b accommodated in the second slot group are connected in series to constitute a partial winding 100, and the wave winding 101a accommodated in the first slot group and the wave winding 101b accommodated in the second slot group are connected in series to constitute a second partial winding 101. Finally, the X-phase winding phase portion 110X is constructed by connecting the partial windings 100 and 101 in parallel.
Moreover, the Y-phase winding phase portion 110Y and the Z-phase winding phase portion 110Z are also constructed in a similar manner to the X-phase winding phase portion 110X.
Automotive alternating-current dynamoelectric machines of this kind are operated over a comparatively wide range of rotational speeds from low speeds to high speeds. Higher harmonic electromagnetic noise in a normal service region from an idling state in which engine rotational speeds are low has a particularly different frequency from the noise of the engine and auxiliary machinery and is heard as a noise that is unpleasant to human ears.
Because the conventional automotive alternating-current dynamoelectric machine is constructed such that the slots are formed at a ratio of two slots per phase per pole at a uniform angular pitch corresponding to an electrical angle of 30 degrees, and the winding phase portions of the stator winding are constructed by connecting in series wave windings having a phase difference corresponding to an electrical angle of 30 degrees, a large 6f electromagnetic vibrational force arises during operation. Thus, one problem has been that electromagnetic noise due to the harmonic components of this 6f electromagnetic vibrational force is large, subjecting passengers to unpleasant sensations.
This conventional automotive alternating-current dynamoelectric machine can also be used in applications where the automotive alternating-current dynamoelectric machine is linked to a shaft of an engine by means of a belt and controlled by an inverter to generate starting torque in the engine. In such cases, another problem has been that vibrations due to the 6f electromagnetic vibrational force are transmitted to the belt, reducing the service life of the belt. During inverter mode at low rotational speeds, where electric power supply is controlled by an inverter unit, since the harmonic components of the 6f electromagnetic vibrational force correspond to the resonance points of the stator, another problem has been that deterioration of the belt service life is particularly promoted.